Organic EL element and organic EL display

ABSTRACT

An organic EL element of the present invention comprises a substrate, an electrode layer, an organic layer, and an electrode layer, whereas the organic layer  3  contains a vinyl polymer obtained by polymerizing a polymerizable monomer containing a compound represented by formula (1) or (2): 
                         
wherein each of L 1  and L 2  is a bivalent group; each of X 1 , X 2 , X 3 , X 4 , X 5 , and X 6  is alkyl group or the like; each of a and e is 0 or 1; each of b, f, g, and h is an integer of 0 to 3; c is an integer of 0 to 2; and d is an integer of 0 to 4.

TECHNICAL FIELD

The present invention relates to an organic EL (electroluminescence)element and an organic EL display.

BACKGROUND ART

In the field of organic EL elements used in organic EL displays and thelike, various devices have been manufactured by way of trial accordingto a technique for forming an organic layer by vacuum deposition using alow molecular weight compound (see, for example, Applied PhysicsLetters, vol. 51, pp. 913 (1987)), and have been in the process ofcoming into practical use.

On the other hand, organic EL elements using polymer materials as aconstituent material for their organic layers have been underdevelopment. In general, such organic EL elements are roughlycategorized into those of π-conjugated type using π-conjugated polymers(see, for example, Japanese Patent Application Laid-Open No. HEI10-92576) and those of molecule dispersion type in which coloringmatters are dispersed in nonconjugated polymers (see, for example,Polymer, vol. 24, pp. 748 (1983) and Applied Physics Letters, vol. 75,No. 1, pp. 4 (1999)). Among them, the nonconjugated organic EL elementsare advantageous in that they can yield a target color with a high colorpurity by mixing a predetermined dopant into a host polymer.

DISCLOSURE OF THE INVENTION

However, polymer materials used in conventional molecule dispersion typeorganic EL elements are not always satisfactory in terms of carriertransportability and stability, whereby the conventional moleculedispersion type EL elements leave a room for improvement in terms ofemission efficiency, heat resistance, and life.

In view of the problems in the prior art mentioned above, it is anobject of the present invention to provide a molecule dispersion typeorganic EL element and organic EL display which can achieve all of theheat resistance, life, and emission efficiency at high levels.

The inventors conducted diligent studies in order to achieve theabove-mentioned object and, as a result, have found that theabove-mentioned problems are overcome by polymerizing a vinyl monomerhaving a specific structure, so as to yield a vinyl polymer, and usingthe polymer as a constituent material of an organic layer.

Namely, the organic EL element in accordance with the present inventioncomprises a substrate, a first electrode layer formed on one side of thesubstrate, an organic layer formed on the first electrode layer, and asecond electrode layer formed on the organic layer; wherein the organiclayer contains a vinyl polymer obtained by polymerizing a polymerizablemonomer containing a compound represented by the following generalformula (1) or (2):

[In the formulae, each of L¹ and L² is a bivalent group; X¹, X², X³, X⁴,X⁵, and X⁶ are either the same or different from each other, eachreferring to alkyl group, alkoxy group, aryl group, aryloxy group,heterocyclic group, amino group, halogen atom, or cyano group; each of aand e is 0 or 1; each of b, f, g, and h is an integer of 0 to 3; c is aninteger of 0 to 2; d is an integer of 0 to 4; and substituents combinedto carbon atoms constituting a fluoranthene ring may be combinedtogether so as to form a ring.]

By polymerizing a polymerizable polymer including a compound representedby the above-mentioned general formula (1) or (2) so as to yield a vinylpolymer and causing an organic layer to contain the vinyl polymer, theorganic EL element of the present invention can enhance thetransportability of holes and electrons injected into the organic layerfrom the first and second electrode layers (the electrontransportability in particular), thereby sufficiently improving theefficiency in emission due to a dopant for luminescence. The vinylpolymer has a high heat resistance and excellent stability, and thus canstably attain a high-level emission efficiency for a long period. Sincethe vinyl polymer in accordance with the present invention has afunction as a dopant for luminescence, the organic layer is not requiredto contain a dopant for luminescence other than the vinyl polymer.However, the organic layer may further contain other dopants forluminescence in order to attain a desirable emission color.

Preferably, in the organic EL element of the present invention, thevinyl polymer is obtained by polymerizing a polymerizable polymercontaining a compound represented by the following general formula (3).Using this vinyl polymer can further enhance the heat resistance, life,and emission efficiency of the organic EL element.

where L¹ is a bivalent group; X¹, X², and X³ are either the same ordifferent from each other, each referring to alkyl group, alkoxy group,aryl group, aryloxy group, heterocyclic group, amino group, halogenatom, or cyano group; a is 0 or 1; b is an integer of 0 to 3; c is aninteger of 0 to 2; d is an integer of 0 to 4; and substituents combinedto carbon atoms constituting a fluoranthene ring may be combinedtogether so as to form a ring.

Preferably, in the organic EL element of the present invention, thevinyl polymer is obtained by polymerizing a polymerizable monomercontaining at least one of a compound represented by the general formula(1) or (3) where L¹ is a substituted or unsubstituted phenylene groupand a is 1, and a compound represented by the general formula (2) whereL² is a substituted or unsubstituted phenylene group and e is 1. Causingan organic layer to contain a vinyl polymer obtained by using a compoundin which a vinyl group and a fluoranthene ring are combined to eachother by way a substituted or unsubstituted phenylene group can furtherenhance the heat resistance, life, and emission efficiency of theorganic EL element.

In the organic EL element of the present invention, the vinyl polymermay be a copolymer of at least one species of the compound representedby one of the general formulae (1) to (3) and at least one species ofvinyl monomer having a structure different from that of the compound.For example, when at least one species of the compound represented bythe general formulae (1) to (3) and at least one other species of vinylmonomer having a carrier transportability are combined together, thedegree of freedom in the molecular design of vinyl polymer for impartinga desirable characteristic to the organic layer becomes greater, theminute adjustment of element characteristics becomes easier, and theheat resistance and life can further be enhanced.

In the organic EL element of the present invention, the organic layermay have a single-layer structure in which the organic layer isconstituted by a luminescent layer alone, but preferably has amultilayer structure including a luminescent layer and an electrontransport layer formed between a layer in the first or second electrodelayer for injecting an electron into the luminescent layer and theluminescent layer. Preferably, in thus configured organic layer, atleast one of the luminescent layer and electron transport layer containsthe vinyl polymer in accordance with the present invention. It will beparticularly preferred if both of the luminescent layer and electrontransport layer contain the vinyl polymer. This can further enhance theheat resistance, life, and emission efficiency of the organic ELelement. The organic EL element of the present invention may furthercomprise a hole transport layer between an electrode for injecting ahole into the luminescent layer and the luminescent layer.

As mentioned above, the organic layer may further contain a dopant forluminescence other than the vinyl polymer in accordance with the presentinvention, and preferably further contains a blue-emitting dopant inparticular. When the organic layer contains both of the vinyl polymer inaccordance with the present invention and the blue-emitting dopant, blueluminescence with a high color purity which has been hard forconventional organic EL elements to achieve can be obtained easily andreliably.

The organic EL display of the present invention comprises a display partin which a plurality of organic EL elements, each constituted by asubstrate, a first electrode layer formed on one side of the substrate,an organic layer formed on the first electrode layer, and a secondelectrode layer formed on the organic layer, are arranged; a powersupply part, electrically connected to the first and second electrodes,for supplying a voltage or current to the first and second electrodes;and a switching part for turning on or off the organic EL elements;wherein the organic layer contains a vinyl polymer obtained bypolymerizing a polymerizable monomer containing a compound representedby the following general formula (1) or (2):

where each of L¹ and L² is a bivalent group; X¹, X², X³, X⁴, X⁵, and X⁶are either the same or different from each other, each referring toalkyl group, alkoxy group, aryl group, aryloxy group, heterocyclicgroup, amino group, halogen atom, or cyano group; each of a and e is 0or 1; each of b, f, g, and h is an integer of 0 to 3; c is an integer of0 to 2; d is an integer of 0 to 4; and substituents combined to carbonatoms constituting a fluoranthene ring may be combined together so as toform a ring.

When the organic EL elements of the present invention are thus arrangedin the display part and driven by the power supply part and switchingpart, an organic EL display which is excellent in luminance and colordisplaying functions and has a high heat resistance and long life can berealized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view showing a preferred embodiment ofthe organic EL element in accordance with the present invention; and

FIG. 2 is a block diagram showing a preferred embodiment of the organicEL display in accordance with the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION

In the following, preferred embodiments of the present invention will beexplained in detail with reference to the drawings as the case may be.In the drawings, constituents identical to each other will be referredto with numerals identical to each other without repeating theiroverlapping explanations. Positional relationships such as upper, lower,left, and right are based on those shown in the drawings unlessotherwise specified. Ratios of dimensions in the drawings are notrestricted to those depicted.

First, a vinyl polymer included in an organic layer in the organic ELelement of the present invention will be explained. The organic layer inaccordance with the present invention includes a polymer (which mayhereinafter be referred to as “vinyl polymer in accordance with thepresent invention” as the case may be) obtained by polymerizing apolymerizable monomer containing a compound represented by the followinggeneral formula (1) or (2), preferably the general formula (3):

The compound represented by the above-mentioned general formula (1) or(2) is one in which a vinyl group, which is a polymerizable functionalgroup, is introduced into fluoranthene or a fluoranthene derivative,which has a high electron mobility, and more specifically one in which agroup represented by -(L¹)_(a)-CH═CH₂ or -(L²)_(e)-CH═CH₂ is combinedwith a carbon atom constituting a fluoranthene ring. When introducing avinyl group to fluoranthene or a fluoranthene derivative, Suzukireaction, Grignard reaction, or the like is used, whereby a targetcompound can be obtained without affecting the vinyl group.

In the formulae, each of L¹ and L² is a bivalent group. Examples of thebivalent group include alkylene groups such as methylene group, ethylenegroup, and propylene group, and arylene groups such as phenylene group.These bivalent groups may have substituent groups or may beunsubstituted. Each of a and e is 0 or 1. When both a and e are 0, astructure in which a vinyl group is directly combined with a carbon atomconstituting a fluoranthene derivative is obtained.

Preferred as the groups represented by -(L¹)_(a)-CH═CH₂ and-(L²)_(e)-CH═CH₂ are those in which each of L¹ and L² is a substitutedor unsubstituted phenylene group while each of a and d is 1 (i.e., asubstituted or unsubstituted vinyl phenylene group). In the substitutedor unsubstituted phenylene group, it will be preferred if the vinylgroup is combined at p-position with respect to a carbon atom of afluorene ring combined with the phenylene group.

Though the position at which the group represented by -(L¹)_(a)-CH═CH₂or -(L²)_(e)-CH═CH₂ is combined with the fluoranthene group is notrestricted in particular, a compound in which the group represented by-(L¹)_(a)-CH═CH₂ is combined with the fluoranthene ring at the3-position, i.e., the compound represented by the following generalformula (3), is preferred:

In the formulae, X¹, X², X³, X⁴, X⁵, and X⁶ are substituent groupscombining with constituent carbons of the fluoranthene ring, each beingalkyl group, alkoxy group, aryl group, aryloxy group, heterocyclicgroup, amino group, halogen atom, or cyano group. On the other hand, b,c, d, f, g, and h refer to respective numbers of X¹, X², X³, X⁴, X⁵, andX⁶, in which each of f, g, and h is an integer of 0 to 3, c is aninteger of 0 to 2, and d is an integer of 0 to 4. When there are aplurality of substituent groups combining with constituent carbons ofthe fluoranthene ring, they may be either the same or different fromeach other. The substituent groups may be combined together to form aring as well.

When the substituent group represented by any of X¹ to X⁶ is an alkylgroup, it may be either straight or branched. The alkyl group ispreferably unsubstituted, but may have a substituent group. The numberof carbons in the alkyl group is preferably 1 to 10. Preferred examplesof the alkyl group include methyl group, ethyl group, n-propyl group,isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butylgroup, and pentyl group.

When the substituent group represented by any of X¹ to X⁶ is an alkoxygroup, it may be either straight or branched. The alkoxy group ispreferably unsubstituted, but may have a substituent group. The numberof carbons in the alkyl group is preferably 1 to 10. Preferred examplesof the alkoxy group include methoxy group, ethoxy group, n-propoxygroup, isopropoxy group, n-butoxy group, isobutoxy group, s-butoxygroup, and t-butoxy group.

When the substituent group represented by any of X¹ to X⁶ is an arylgroup, it may be either substituted or unsubstituted. The total numberof carbons in the aryl group is preferably 6 to 20. Preferred examplesof the aryl group include phenyl group, o-tolyl group, m-tolyl group,p-tolyl group, and biphenylyl group.

When the substituent group represented by any of X¹ to X⁶ is an aryloxygroup, it may be either substituted or unsubstituted. The total numberof carbons in the aryloxy group is preferably 6 to 20. Preferredexamples of the aryloxy group include phenoxy group, o-tolyloxy group,m-tolyloxy group, and p-tolyloxy group.

When the substituent group represented by any of X¹ to X⁶ is aheterocyclic group, it is preferably a 5- or 6-membered ring. Theheterocyclic ring may have either a condensed ring or substituent group.The heterocyclic ring may be either aromatic or nonaromatic. Examples ofthe heterocyclic ring include pyrrolyl group, pyridyl group, quinolylgroup, thienyl group, and furyl group.

When the substituent group represented by any of X¹ to X⁶ is a halogenatom, its examples include fluorine, chlorine, bromine, and iodine.

When the substituent group represented by any of X¹ to X⁶ is an aminogroup, the amino group may be either substituted or unsubstituted, andmay have the above-mentioned alkyl or aryl group, for example. The totalnumber of carbons in the amino group is preferably 0 to 20. Preferredexamples of the amino group include amino group (—NH₂) in the narrowsense, methylamino group, ethylamino group, phenylamino group,dimethylamino group, and diphenylamino group.

In the compound represented by any of general formulae (1) to (3), itwill be preferred in particular if the fluoranthene ring has nosubstituent group or any of substituent groups of alkyl group, alkoxygroup, and aryl group (more preferably alkyl group or aryl group).

Among the compounds represented by general formula (1) or (2), thoserepresented by the following formulae (4) to (48) are used preferably,and those represented by the following formulae (5), (7), (8), (9),(10), (11), (12), (28), (29), (30), (31), (32), (33), (34), (37), (38),(39), (40), (41), (46), (47), and (48) are used more preferably. Fromthe viewpoint of solubility, compounds represented by the followingformulae (5), (7), (31), (32), (34), (37), (38), and (40) are usedpreferably in particular.

The vinyl polymer in accordance with the present invention may be ahomopolymer of one species of the compounds represented by theabove-mentioned general formula (1) or (2), or a copolymer of at leasttwo species of the compounds represented by the above-mentioned generalformula (1) or (2). Namely, this polymer is one having at least one ofconstituent units represented by the following general formulae (49) and(50):

The polymer may be a copolymer formed between a compound represented bythe above-mentioned general formula (1) or (2) and a vinyl monomerhaving a structure different from that of the compound. For example, forfurther enhancing the electron transportability of the polymer,4-vinylpyridine represented by the following formula (51),2-vinylpyridine represented by the following formula (52),1-vinylimidazole represented by the following formula (53), and the likecan be used therewith. For further enhancing the hole transportabilityof the polymer, N-vinylcarbazole represented by the following formula(54), (4-vinlylphenyl)diphenylamine represented by the following formula(55), and the like may be used therewith. The ratio of the vinyl monomeris not restricted in particular, but is preferably 1 to 50 mol %, morepreferably 1 to 30 mol %, based on the total amount of the polymerizablemonomers constituting the polymer.

The method of polymerizing the compound represented by theabove-mentioned general formula (1) or (2) is not restricted inparticular, whereby the compound can easily be combined by radicalpolymerization, cationic polymerization, anionic polymerization, or thelike. The weight-average molecular weight of the resulting polymer ispreferably 10,000 to 1,000,000.

In the present invention, the organic layer in the organic EL element iscaused to contain the polymer, whereby the transportability of holes andelectrons injected into the organic layer from the first and secondelectrode layers (the electron transportability in particular) can beenhanced, so as to sufficiently improve the emission efficiency. Thispolymer has a high heat resistance and excellent stability, and thus canstably attain a high-level emission efficiency for a long period.

The reason why the above-mentioned polymer is excellent in carriertransportability, heat resistance, and stability is not definitelyclear, but is presumed by the inventors as follows. In the polymer,obtained by the compound represented by the general formula (1) or (2),having the constituent unit represented by the general formula (49) or(50), it seems that a helical structure is formed by a polyvinyl chain,whereas a plurality of fluoranthene rings are arranged at predeterminedintervals in an overlapping fashion on the outside of the helicalstructure, whereby a cyclic structure which is effective in carriertransportability (electron transportability in particular) and stablecan be attained.

The organic EL element of the present invention will now be explained.

FIG. 1 is a schematic sectional view showing a preferred embodiment ofthe organic EL element in accordance with the present invention. In theorganic EL element 9 shown in FIG. 1, an anode layer 2 (first electrodelayer) and an insulator layer 6 are laminated in this order on asubstrate 1, whereas a part of the insulator layer 6 corresponding to aluminescent part is provided with an opening at which the anode layer 2is exposed. An organic layer 3 and a cathode layer 4 (second electrodelayer) are laminated on thus exposed anode layer 2, so as to form alaminate structure of the substrate 1/anode layer 2/organic layer3/cathode layer 4. The organic layer 3 contains a dopant forluminescence and a vinyl polymer obtained by polymerizing apolymerizable monomer containing a compound represented by theabove-mentioned general formula (1) or (2). The face of the organic ELelement 9 on the cathode layer 2 side is sealed with a sealing plate 5by way of a spacer 7 disposed on the insulator layer in thenonluminescent region.

Substrate

Employable as the substrate 1 are amorphous substrates made of glass,silica, and the like; crystal substrates made of Si, GaAs, ZnSe, ZnS,GaP, InP, and the like; metal substrates made of Mo, Al, Pt, Ir, Au, Pd,SUS, and the like; etc. Also usable are those in which thin films madeof crystalline or amorphous ceramics, metals, organic matters, and thelike are formed on predetermined substrates.

When the side of the substrate 1 is employed as the light outlet side, atransparent substrate made of glass, silica, or the like is preferablyused as the substrate 1. It will be preferred in particular if atransparent substrate made of inexpensive glass is used. For adjustingthe emitted color light, the transparent substrate may be provided witha color filter film, a color-converting film containing a phosphormaterial, a dielectric reflecting film, or the like.

Anode Layer

The anode layer 2 functions as an electrode for injecting holes into theorganic layer 3. To this aim, a material which can efficiently injectholes into the organic layer is preferred as the material for the anodelayer 2. More specifically, a material having a work function of 4.5 to5.4 eV is preferred.

When the side of the substrate 1 is employed as the light outlet side,the transmittance of the organic EL element in the wavelength region of400 to 700 nm, which is the luminescent wavelength region thereof, atthe respective wavelengths of RGB colors in particular, is preferablynot less than 50%, more preferably not less than 80%, further preferablynot less than 90%. When the transmittance of the anode layer 2 is lessthan 50%, the emission from the organic layer 3 is attenuated, whereby aluminance required for displaying images is harder to attain.

The anode layer exhibiting a high light transmittance can be constructedby a transparent conductive film constituted by various oxides.Preferred as such a material are indium oxide (In₂O₃), tin oxide (SnO₂),zinc oxide (ZnO), tin-doped indium oxide (ITO), zinc-doped indium oxide(IZO), and the like. Among them, ITO is particularly preferred in that athin film having a uniform resistivity within a plane can easily beobtained. The ratio of SnO₂ to In₂O₃ in ITO is preferably 1 to 20 wt %,more preferably 5 to 12 wt %. The ratio of ZnO to In₂O₃ in IZO ispreferably 12 to 32 wt %. The materials mentioned above may be usedsingly or in combination of two or more species.

The composition of the oxide constituting the anode layer 2 may somewhatdeviate from its stoichiometric composition. For example, though ITOusually contains In₂O₃ and SnO₂ in a stoichiometric composition, it willbe sufficient if x and y fall within the ranges of 1.0 to 2.0 and 0.8 to1.2, respectively, when the composition of ITO is represented byInO_(x)·SnO_(y).

Adding a transparent dielectric such as silicon oxide (SiO₂) to theanode layer 2 can adjust the work function of the anode layer 2. Forexample, adding about 0.5 to 10 mol % of SiO₂ to ITO can enhance thework function of ITO, so that the work function of the anode layer 2falls within the preferred range mentioned above.

Preferably, the thickness of the anode layer 2 is determined in view ofthe above-mentioned light transmittance. For example, when an oxidetransparent conductive film is used, its thickness is preferably 50 to500 nm, more preferably 50 to 300 nm. When the thickness of the anodelayer 2 exceeds 500 nm, the light transmittance may become insufficient,while the anode layer 2 may peel off from the substrate 1. The lighttransmittance improves as the thickness decreases. When the filmthickness is less than 50 nm, however, the efficiency of hole injectioninto the organic layer 3 drops, while the film strength decreases.

Though FIG. 1 shows an example of organic EL element in which the anode2 is disposed on the substrate 1, whereas the cathode layer 4 isarranged on the side remote from the substrate 1 by way of the organiclayer 3, the positions of the anode layer 2 and cathode layer 4 may bereversed. When the cathode layer 4 is disposed on the substrate 1, thecathode layer 4 side can be employed as the light outlet side. It willbe preferred in this case if the cathode layer 4 satisfies the opticaland thickness conditions mentioned above.

Insulator Layer

Preferably, in the organic EL element of the present invention, theinsulator layer 6 is disposed in the nonluminescent region on the anodelayer 2. Providing the insulator layer 6 can regulate the luminescentarea, so as to restrain colors from blurring. For the material of theinsulator layer 6, general insulator film materials such as SiO₂ andAl₂O₃, for example, can selectively be used as appropriate. Thethickness of the insulator layer 6 is preferably about 1 to 7 μm. Thepart of the insulator layer 6 corresponding to the luminescent region isprovided with an opening by a technique of lithography or etching suchthat the anode layer 2 is exposed, whereas the organic layer 3 and thecathode layer 4 (second electrode layer) are laminated in this order onthe exposed anode layer 2. This secures electric conduction between theanode layer 2 and organic layer 3.

Organic Layer

The organic layer 3 is a luminescent layer containing a dopant forluminescence and the vinyl polymer in accordance with the presentinvention as mentioned above.

The dopant for luminescence can be selected as appropriate according totarget emission colors. For example, as a phosphorescent dopant, iridiumcomplexes such as tris(2-phenylpyridine) iridium (Ir(ppy)₃), platinumcomplexes having a porphyrin ring such as 2, 3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum (PtOEP), and thelike can be used. As a blue-emitting dopant, tetraphenyl butadiene andits derivatives, styrylamine derivatives, fluoranthene derivatives, andthe like can be used. The ratio of the dopant for luminescence to thetotal amount of the polymerizable monomer before polymerization ispreferably 1 to 15 wt %. Since the vinyl polymer in accordance with thepresent invention has a function as a luminescent dopant, the organiclayer 3 is not required to include any luminescent dopant other than thevinyl polymer in accordance with the present invention.

The organic layer 3 contains the luminescent dopant and the vinylpolymer in accordance with the present invention, and may furthercontain other carrier-transporting materials such as hole-transportingmaterials and electron-transporting materials.

Any of low and high molecular weight materials can be used as ahole-transporting material. Examples of hole-transporting low molecularweight materials include pyrazoline derivatives, arylamine derivatives,stilbene derivatives, and triphenyldiamine derivatives. Examples ofhole-transporting high molecular weight materials includepolyvinylcarbazole, polyethylene dioxythiophene/polystyrene sulfonatecopolymer (PEDOT/PSS), and polyaniline/polystyrene sulfonate copolymer(Pani/PSS). These hole-transporting materials may be used singly or incombination of two or more species.

Any of low and high molecular weight materials can be used as anelectron-transporting material. Examples of electron-transporting lowmolecular weight materials include oxadiazole derivatives,anthraquinodimethane and its derivatives, benzoquinone and itsderivatives, naphthoquinone and its derivatives, anthraquinone and itsderivatives, tetracyanoanthraquinodimethane and its derivatives,fluorene and its derivatives, diphenyldicyanoethylene and itsderivatives, phenanthroline and its derivatives, and metal complexesincluding these compounds as ligands. Examples of electron-transportinghigh molecular weight materials include polyquinoxaline andpolyquinoline. These electron-transporting materials may be used singlyor in combination of two or more species.

For the low molecular weight materials and their modes of use,techniques disclosed in Japanese Patent Application Laid-Open Nos. SHO63-70257, SHO 63-175860, HEI 2-135359, HEI 3-37992, HEI 3-152184, andthe like can be used, for example.

The organic layer 3 can favorably be formed by coating. Employed at thetime of coating is a coating liquid in which a dopant for luminescence,the vinyl polymer in accordance with the present invention, and othercarrier-transporting materials used as necessary are added to apredetermined solvent. The solvent in the coating liquid is notrestricted in particular as long as it is one adapted to dissolve thevinyl polymer in accordance with the present invention and does notgenerate any obstacle at the time of coating. For example, organicsolvents such as those based on alcohols, hydrocarbons, ketones, andethers can be used. Preferred among them are chloroform, methylenechloride, dichloroethane, tetrahydrofuran, toluene, xylene,cyclohexanone, dimethylformamide, N-methylpyrrolidone, and the like. Theamount of the vinyl polymer in accordance with the present inventiondissolved in the solvent is appropriately selected according to thestructure, molecular weight, and the like of the vinyl polymer, and ispreferably not less than 0.1 wt %.

The coating liquid is applied so as to cover the opening of theinsulator layer 6 at which the anode layer 2 is exposed, and the solventis eliminated from the coating liquid, whereby the organic layer 3 isformed. Though the method of coating with the coating liquid is notrestricted in particular, spin coating, spray coating, dip coating, inkjetting, and printing, for example, are employable. The solvent can beeliminated from the coating liquid by heating and drying preferably at atemperature of 30 to 200° C., more preferably at a temperature of 60 to100° C. under reduced pressure or in an inert gas atmosphere.

The thickness of the organic layer 3 is not restricted in particular andmay vary depending on its forming method, but is preferably 5 to 500 nm,more preferably 10 to 300 nm.

Though FIG. 1 shows an example of organic EL element in which theorganic layer 3 has a single-layer structure solely constituted by aluminescence layer containing a dopant for luminescence and the vinylpolymer in accordance with the present invention, the organic layer inthe organic EL element of the present invention may have a multilayerstructure in which a plurality of layers are laminated.

An example of the organic layer having a multilayer structure is one inwhich a hole transport layer is disposed between a luminescent layer andan anode layer, whereas an electron transport layer is disposed betweenthe luminescent layer and a cathode layer, whereby the hole transportlayer, luminescent layer, and electron transport layer are laminated inthis order from the side closer to the anode layer. This can regulateabilities of the anode and cathode layers to inject holes and electronsinto the luminescent layer, and the mobility of their electric charges.In such an organic layer having a multilayer structure, while theabove-mentioned hole- and electron-transporting materials can be used asrespective materials for the hole and electron transport materials, itwill be preferred if at least one of the luminescent layer and electrontransport layer contains the vinyl polymer in accordance with thepresent invention. It will be preferred in particular if both of theluminescent layer and electron transport layer contain the polymer. Thiscan further enhance the heat resistance, life, and emission efficiencyof the organic EL element.

Cathode Layer

The cathode layer 4 functions as a layer for injecting electrons intothe organic layer 3. Specific modes of the cathode layer includeinorganic electron injection layers, electron injection layers made ofcoating films of organic metal complexes, and electron injection layersmade of coating films of metal salts. A laminate made of these electroninjection layers and an auxiliary electrode layer laminated thereon mayalso be employed as the cathode layer 4. In this laminate, the inorganicelectron injection layers, coating films of organic metal complexes, andcoating films of metal salts are disposed on the side closer to theorganic layer 3, whereas the auxiliary electrode layer is arranged onthe side farther from the organic layer 3.

When forming an inorganic electron injection layer, an inorganicmaterial having a low work function is preferably selected in order tomake it easier to inject electrons into the organic layer 3. Examples ofthe inorganic material include alkali metals such as Li, Na, K, and Cs;alkaline-earth metals such as Mg, Ca, Sr, and Ba; and alkali halidessuch as LiF and CsI. Also, metals having characteristics similar tothose of alkali metals or alkaline-earth metals such as La, Ce, Sn, Zn,and Zr can be used. Among them, Ca is preferred in particular because ofits very low work function.

The thickness of the inorganic electron injection layer is notrestricted in particular as long as electrons can be injected into theorganic layer 3, but is preferably 0.1 to 100 nm, more preferably 1.0 to50 nm, when an alkali metal or alkaline-earth metal is used. When analkali halide is used, the thickness is preferably as small as possiblefrom the viewpoint of the capability of injecting electrons into theorganic layer 3. Specifically, the thickness is preferably not more than10 nm, more preferably not more than 1 nm.

The electron injection layer constituted by a coating film of an organicmetal complex can be formed, for example, by coating the organic layer 3with a coating liquid in which an organic metal complex is added to apredetermined solvent by a coating method such as spin coating and theneliminating the solvent. As the organic metal complex, β-diketonatocomplexes, quinolinol complexes, and the like can be used. The metal inthe organic metal complex is not restricted in particular, examples ofwhich include alkali metals such as Li, Na, K, and Cs; alkaline-earthmetals such as Mg, Ca, Sr, and Ba; and metals such as La, Ce, Sn, Zn,and Zr having characteristics similar to those of alkali metals oralkaline-earth metals. Causing the coating film of the organic metalcomplex to further contain an electron-transporting high molecularweight material and the like can further improve electriccharacteristics of the electron injection layer and its adhesion to theorganic layer 3. From the viewpoint of capability of injecting electronsinto the organic layer 3, the thickness of the electron injection layerconstituted by a coating film of an organic metal complex is preferablyas small as possible. Specifically, the thickness is preferably not morethan 10 nm, more preferably not more than 1 nm.

The total thickness of the electron injection layer constituted by thecoating film of the organic metal complex and a protective electrodelayer, i.e., the thickness of the whole cathode layer 4, is notrestricted in particular as long as electrons can be injected into theorganic layer 3, but is preferably 50 to 500 nm. The effects mentionedabove are less likely to be obtained sufficiently when the thickness ofthe protective electrode layer is too small as compared with theelectron injection layer. When the thickness of the auxiliary electrodeis too large, the stress caused by the auxiliary electrode layer tendsto increase so much that the growing rate of dark spots becomes higher.

The electron injection layer constituted by a coating film of a metalsalt can be formed, for example, by coating the organic layer 3 with acoating liquid in which a metal salt is added to a predetermined solventby a coating method such as spin coating and then eliminating thesolvent. Examples of the metal contained in the metal salt include Ag,Al, Au, Be, Bi, Co, Cu, Fe, Ga, Hg, Ir, Mo, Mn, Nb, Ni, Os, Pb, Pd, Pt,Re, Ru, Sb, Sn, Ti, and Zr.

The metal salt may be any of organic and inorganic metal salts. Examplesof the organic meal salts include substituted or unsubstituted aliphaticcarboxylic salts, dicarboxylic acid salts, aromatic carboxylic acidsalts, alcoholates, phenolates, and dialkylamides. Examples of theinorganic metal salts include halides.

The aliphatic carboxylic acid in the aliphatic carboxylic acid salts maybe any of saturated and unsaturated aliphatic carboxylic acids. Examplesof the saturated aliphatic carboxylic acid salt include metal salts ofacetic acid, propionic acid, octanoic acid, isooctanoic acid, decanoicacid, and lauric acid. Examples of unsaturated aliphatic carboxylic acidsalt include metal salts of oleic acid, ricinoleic acid, and linolicacid.

Examples of the dicarboxylic acid salts include metal salts ofdicarboxylic acids such as citric acid, malic acid, and oxalic acid.

Examples of the aromatic carboxylic acid salts include metal salts ofbenzoic acid, o-tert-butylbenzoic acid, m-tert-butylbenzoic acid,p-tert-butylbenzoic acid, salicylic acid, m-hydroxybenzoic acid, andp-hydroxybenzoic acid. Preferred among them are metal salts of salicylicacid.

The alcoholates are metal salts of alcohols. Examples of alcoholcomponents constituting the alcoholates include primary alcohols such asethanol, n-propyl alcohol, and n-butyl alcohol; secondary alcohols suchas isopropyl alcohol and isobutyl alcohol; and tertiary alcohols such astert-butyl alcohol.

The phenolates are metal salts of phenols. The number of hydroxyl groupsin the phenol component constituting a phenolate is not restricted inparticular, but is preferably 1 or 2. The phenol compound may furtherinclude a substituent group (which is preferably a straight or branchedalkyl group having a carbon number of 1 to 8) in addition to thehydroxyl groups. Preferably used in the present invention are phenol,naphthol, 4-phenylphenol, and the like.

Examples of halides which are inorganic metal salts include metal saltsof chlorine, fluorine, bromine, and iodine.

Preferably, an auxiliary electrode layer is disposed on these electroninjection layers. This can improve the efficiency at which electrons areinjected into the organic layer 3, and prevent moisture or organicsolvents from entering the organic layer 3 or electron injection layers.Though common metals can be used as a material of the auxiliaryelectrode layer since there are no restrictions on the work function andelectric charge, metals which are easy to handle while having a highconductivity are preferably used. When the electron injection layercontains an organic material in particular, it will be preferred if thematerial of the auxiliary electrode layer is appropriately selectedaccording to the species and adhesion of the organic material. Specificexamples of the material used in the auxiliary electrode layer includeAl, Ag, In, Ti, Cu, Au, Mo, W, Pt, Pd, and Ni. Using low-resistancemetals such as Al and Ag among them can further enhance the electroninjection efficiency. Using a metal compound such as TiN can yield afurther higher sealability. These materials may be used singly or incombination of two or more species. Two or more species of the metal maybe used as an alloy.

Spacer and Sealing Plate

Sealing the cathode layer 4 side of the organic EL element 9 with thesealing plate 5 as shown in FIG. 1 can prevent not only the organiclayer 3 but also the anode layer 2 and cathode layer 4 fromdeteriorating. Here, arranging the spacer 7 in the nonluminescent regionon the insulator layer 6 and bonding the spacer 7 to the sealing plate 5can prevent the surface on the cathode layer 4 side of the organic ELelement 9 and the sealing plate 5 from coming into contact with eachother. The spacer 7 may be made of any of organic and inorganicmaterials (including metal materials). The spacer 7 can also be formedfrom a photosensitive material such as photoresist or photosensitivepolyimide by a technique such as photolithography. An adhesive and aninsulator such as glass spacer may be mixed together, and the resultingmixture may be applied to a region where the spacer 7 is to be formed.

Preferably, a sealing gas is inserted into a space formed by the surfaceof the organic EL element 9 on the cathode layer 4 side, the sealingplate 5 and the spacer 7. Preferably used as the sealing gas are inertgases such as Ar and He. The moisture content in the sealing gas ispreferably not more than 100 ppm, more preferably not more than 10 ppm,further preferably not more than 1 ppm. The lower limit for the moisturecontent in the sealing gas is not restricted in particular, but a lowerlimit of about 0.1 ppm is quite favorable in that its effect ofpreventing the organic layer 3, anode layer 2, cathode layer 4, and thelike from deteriorating is high.

The above-mentioned embodiment can enhance the transportability of holesand electrons injected into the organic layer from the first and secondelectrode layers (the electron transportability in particular) bycausing the organic layer 3 to contain the vinyl polymer in accordancewith the present invention, thereby sufficiently improving the emissionefficiency. This vinyl polymer has a high heat resistance and excellentstability, and thus can stably attain a high-level emission efficiencyfor a long period. This organic EL element is quite useful in variousfields of light-employing devices such as organic EL displays, opticalpickups used for reading and writing memories, repeaters disposed intransmission lines for optical communications, and photocouplers.

The organic EL display of the present invention will now be explained.

FIG. 2 is a block diagram showing a preferred embodiment of the organicEL display. The organic EL display shown in FIG. 2 is a passive-driving,color conversion type organic EL element using a blue-emitting elementas a pumping light source. The color conversion type refers to a methodin which three-color fluorescent elements are pumped with visible lightemissions of high-energy lines. In the color conversion method, theorganic layer in the organic EL element is often caused to generate ablue emission, which is then used as a pumping light energy line so asto pump green and red fluorescent surfaces, thereby yielding green lightand red light. This method is known as the color conversion method,since blue is converted into green and red.

In FIG. 2, a display part 14 is one in which a plurality of organic ELelements 9, each constituted by a substrate 1, an anode layer 2 (firstelectrode layer) formed on one side of the substrate 1, an organic layer3 formed on the anode layer 2, and a cathode layer 4 (second electrodelayer), are arranged two-dimensionally. In each of the organic ELelements 9, three organic layers 3 (luminescent layers), each containingthe vinyl polymer in accordance with the present invention and a dopantfor blue luminescence, are formed so as to correspond to threeluminescent regions (e.g., 13 a, 13 b, 13 c). In the three luminescentregions, one is a blue-emitting region, whereas the remaining two aregreen- and red-emitting regions.

Preferred examples of the material for the substrate 1 includetransparent or semitransparent materials such as glass, silica, andresins.

On the substrate 1, fluorescent conversion filter films are provided inregions corresponding to two of the three luminescent regions formed ina single organic EL element as mentioned above, and regulate emissioncolors, whereby these regions become green- and red-emitting regions,respectively. The luminescent region provided with no fluorescentconversion filter film is a blue-emitting region.

Each fluorescence conversion filter film, which absorbs light due to anelectric field emission in the organic layer 3 and causes a phosphor inthe film to release light having a color different from that of theabsorbed light, thereby converting emission colors, includes thephosphor, an optical absorber, and a binder in general. The fluorescenceconversion filter film can be formed by patterning using a techniquesuch as lithography or printing. In this case, the material of thefluorescence conversion filter film is preferably one which can formfine patterning, or one which is less likely to be damaged in the stepof forming the upper layer (anode layer 2 or the like).

The phosphor contained in the fluorescent conversion filter film ispreferably one with a high fluorescent quantum yield, or one exhibitinga high optical absorptivity in the luminescent wavelength region of theluminescent element as with laser coloring matters. Examples of thephosphor include rhodamine-based compounds, perylene-based compounds,cyanine-based compounds, phthalocyanine-based compounds includingsubphthalocyanine and the like, naphthaloimide-based compounds,condensed cyclic hydrocarbon-based compounds, condensed heterocycliccompounds, styryl-based compounds, and coumarin-based compounds. Whenthe phosphor itself has an insufficient optical absorptivity, an opticalabsorber is preferably used together therewith, whereas one which doesnot quench the fluorescence is preferred as the optical absorber.

The binder is not restricted in particular as long as it does not quenchthe fluorescence, and can be used selectively from among known binders.

It will be preferred if a color filter for cutting off external lighthaving a short wavelength which can be absorbed by constituent materialsof the organic EL element 9 or the fluorescence conversion filter filmis combined with the fluorescence conversion filter film, since it canfurther improve the light resistance of the element or its displaycontrast.

In the display part 14, two anode layers 2 are formed in parallel witheach other on the substrate 1 and fluorescence conversion filter film soas to pass the three luminescent regions 13 a to 13 c in the organic ELelement 9. Here, the anode layer 2 is arranged such that the luminescentregions 13 a to 13 c are not completely covered therewith, whereby eachof the luminescent regions 13 a to 13 c is partly exposed. Each of theanode layers 2 is a common electrode for a plurality of (2 in FIG. 2)organic EL elements, whereas a power supply part 8, which will beexplained later, is electrically connected to one end each of the anodelayers 2. Such stripe-like anode layers 2 can be formed, for example, byforming an ITO film on the substrate 1 having a fluorescence conversionfilter film patterned thereon and then carrying out patterning andetching.

Though not illustrated in detail, it will be preferred if an insulatorlayer such as SiO₂ layer or Al₂O₃ layer is provided on the anode layer 2after the latter is formed. Preferably, the region of the insulatorlayer corresponding to the luminescent region is opened by etching, andthe organic layer 3 is formed in the opening.

In the display part 14, the organic layers 3 containing the vinylpolymer in accordance with the present invention and the dopant for blueluminescence are formed in conformity to the individual luminescentregions of the organic EL element 9 so as to cover the individualluminescent regions while riding across the anode layers 2. The organiclayers 3 can preferably be formed by a coating method such as spincoating.

In the display part 14, six cathode layers 4 are formed in conformity tothe luminescent regions of the organic EL element 9 so as to pass overthe organic layers 3. Each of the cathode layers 4 is a common electrodefor a plurality of (2 in FIG. 2) organic EL elements, whereas aswitching part 10 which will be explained later is connected to one endeach of the cathode layers 4.

In the passive driving type organic EL display as in this embodiment, itwill be preferred if the stripe-like anode layers 2 and stripe-likecathode layers 4 are arranged orthogonal to each other as shown in FIG.2. Here, intersections between the anode layers 2 and cathode layers 4in the luminescent regions correspond to respective pixels in thedisplay.

In the nonluminescent regions of the display part 14, each organic ELelement 9 is provided with a spacer 7. Bonding a sealing plate (notdepicted) to the spacer 7 seals the surface on the cathode layer 4 side

In the organic EL display shown in FIG. 2, a driving part 11 forcontrolling the displaying in the display part 14 includes the powersupply part 8 for supplying a current or voltage to the anode layers 2and cathode layers 4, the switching part 10 for sending an on/offcontrol signal to the organic EL elements 9, and a control logicalcircuit 12 for them. The power supply part 8 is electrically connectedto the anode layers 2, the switching part 10 is electrically connectedto the cathode layers 4, and the power supply part 8 and switching part10 are electrically connected to each other by way of the controllogical circuit 12. The scheme of driving the organic EL device 9 in thedisplay part 14 is not restricted in particular, whereby DC driving,pulse driving, or AC driving, for example, can be employed. It will bepreferred if a DC, pulsed, or AC current or voltage is supplied at thetime of driving, whereas the applied voltage is preferably about 2 to 30V.

By causing the organic layer 3 to contain the vinyl polymer inaccordance with the present invention and the blue-emitting dopant, theabove-mentioned embodiment can yield a blue emission with a high colorpurity in the luminescent regions and keep this characteristic stablyfor a long period. The blue emission is taken out as it is from thesubstrate 1 side in the blue-emitting region. In the green and redluminescent regions, by pumping respective phosphors corresponding togreen and red in the fluorescence conversion filter films with the blueemission employed as a pumping light energy line, green light and redlight are taken out from the substrate 1 side. Therefore, thisembodiment can realize an organic EL display which is excellent inluminance and color displaying functions and has a high heat resistanceand a long life.

The organic EL display of the present invention is not restricted to theabove-mentioned embodiment, but can be determined in view of theluminance, life, power consumption, and cost required for a targetdisplay product. For example, though FIG. 2 shows a so-called passivedriving type organic EL display, the organic EL display of the presentinvention may be an active driving type full-color display using apolysilicon TFT or the like.

When the organic EL display of the present invention is a full-colordisplay, full-color displaying is realized by forming three primarycolor elements of red, green, and blue (RGB). Here, the full-colordisplaying scheme may be not only the color conversion shown in theabove-mentioned embodiment, but also any of RGB three-colorjuxtaposition, white luminescence method, and the like. The RGBthree-color juxtaposition is a display scheme in which each of the RGBthree-color luminescent elements is caused to emit light. The whiteluminescence method is a scheme in which a three-color filter used in aliquid crystal display device or the like cuts off a part of thewavelength of white luminescence, so as to realize full-colordisplaying. The white luminescence and color conversion methods make itunnecessary to prepare three-color luminescent elements, and thus cansimplify the forming of luminescent elements and easily achieve a largerarea.

By appropriately selecting a dopant for luminescence added to theluminescent layer of the organic EL element, the organic EL display ofthe present invention can employ any of the above-mentioned colordisplay schemes. For example, when the organic layer of the organic ELelement is caused to contain a dopant for blue luminescence, so as toyield a luminescent layer, the color conversion scheme can favorably beemployed. When the organic layer of the organic EL element is caused tocontain a dopant for phosphorescence, the RGB three-color juxtapositionmethod based on phosphorescence can favorably be employed.

EXAMPLES

The present invention will now be explained in further detail withreference to examples and comparative examples, though the presentinvention is not restricted to the following examples at all.

Example 1

In air atmosphere, 12.5 g (53.6 mmol) of 5-bromoacenaphthene representedby the following formula (56) and 13.4 g (59 mmol) of2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) represented by thefollowing formula (57) were dissolved in 100 ml of toluene, and werecaused to react for 6 hours at 130° C. The resulting crude product wasextracted with hexane, and then was refined with column chromatography,whereby 6.0 g of 5-bromoacenaphthylene represented by the followingformula (58) were obtained as a yellow solid.

Next, 4.3 g (18.5 mmol) of thus obtained 5-bromoacenaphthylene and 5.0 g(18.5 mmol) of 1,3-diphenylbenzofuran represented by the followingformula (59) were dissolved in 100 ml of toluene in nitrogen atmosphere,and they were caused to react for 24 hours at 120° C. After toluene wasevaporated away from the reaction liquid, the residue was caused toreact with 150 ml (18.5 mmol) of acetic acid added thereto for 1 hour at145° C. in nitrogen atmosphere. The reactant was further caused to reactwith hydrogen bromide added thereto for 30 minutes at 110° C. Theresulting crude product was refined with column chromatography, whereby3.5 g of 3-bromo-7,12-diphenylbenzofluoranthene represented by thefollowing formula (60) were obtained as a yellow solid.

Subsequently, in nitrogen atmosphere, 3.4 g (7.0 mmol) of thus obtained3-bromo-7,12-diphenylbenzofluoranthene, 1.6 g (10.0 mmol) of4-vinylphenylboronic acid represented by the following formula (61), and0.25 g of tetrakis(triphenylphosphino)palladium (Pd(pph₃)₄) weredissolved in a mixed solvent constituted by 15 ml of toluene and 4 ml ofethanol, so as to yield a solution. To thus obtained solution, 8 ml of2-M aqueous sodium carbonate solution were added, and they were causedto react for 24 hours at 90° C. The resulting crude product wasextracted with ether and then refined with column chromatography,whereby 3.1 g of 3-(4-vinylphenyl)-7,12-diphenylbenzofluoranthenerepresented by formula (7) were obtained as a pale yellow solid. Thestructure of thus obtained3-(4-vinylphenyl)-7,12-diphenylbenzofluoranthene was identified bynuclear magnetic resonance (NMR), infrared absorption analysis (IR), andmass spectrometry (MS).

Next, 2 g of 3-(4-vinylphenyl)-7,12-diphenylbenzofluoranthene and 20 mgof benzoyl peroxide (BPO) as a radical polymerization initiator weredissolved in 15 ml of tetrahydrofuran (THF), and were held at 70° C. for48 hours in nitrogen atmosphere, so as to effect a polymerizationreaction. After the completion of the reaction, reprecipitation wascarried out three times by using THF and methanol as good and poorsolvents, respectively, and then similar reprecipitation was performedthree times with the poor solvent replaced by ethyl acetate, whereby1.73 g of a vinyl polymer whose monomer unit was3-(4-vinylphenyl)-7,12-diphenylbenzofluoranthene were obtained. Theweight-average molecular weight of thus obtained vinyl polymer was49,000.

A 2-wt % toluene solution of thus obtained vinyl polymer was preparedand employed as a luminescent layer forming coating liquid.

A coating liquid containing a polyethylene dioxythiophene/polystyrenesulfonic acid copolymer (PEDOT/PSS) including constitutional unitsrepresented by the following formulae (62) to (64) was applied by spincoating onto a substrate formed with an ITO film as an anode layer, andwas dried in vacuum for 5 minutes at 110° C., so as to form a holetransport layer having a thickness of 500 Å. Subsequently, theabove-mentioned luminescent layer forming coating liquid was appliedonto the hole transport layer, and was dried in vacuum for 5 minutes at110° C., so as to form a luminescent layer having a thickness of 1,000Å. On this luminescent layer, an LiF layer (having a thickness of 6 Å)as an electron injection layer and an Al layer (having a thickness of2,500 Å) as an auxiliary electrode were deposited in vacuum in thisorder, so as to form a cathode layer, and the surface on the cathodelayer side was sealed, whereby the aimed organic EL element wasobtained.

Thus obtained organic EL element yielded blue luminescence due to thevinyl polymer including 3-(4-vinylphenyl)-7,12-diphenylbenzofluorantheneas a monomer unit, whereas its current efficiency was 0.8 cd/A at thetime of constant-current driving at 10 mA/cm². When a life test wasconducted by constant-current driving at 10 mA/cm², the life untilluminance decreased by half (luminance half-life as in the following)was 180 hours.

Example 2

Polyvinylcarbazole (PVK) represented by the following formula (65) as ahole-transporting host polymer and the vinyl polymer (vinyl monomercontaining 3-(4-vinylphenyl)-7,12-diphenylbenzofluoranthene as a monomerunit) obtained by Example 1 were blended at a molar ratio of 70:30. A2.0-wt % toluene solution of this blend was prepared, so as to yield aluminescent layer forming coating liquid.

An organic EL element was produced in a manner similar to Example 1except that a luminescent layer was formed by using thus obtainedcoating liquid. The resulting organic EL element yielded blueluminescence due to the vinyl polymer including3-(4-vinylphenyl)-7,12-diphenylbenzofluoranthene as a monomer unit,whereas its current efficiency was 1.0 cd/A at the time ofconstant-current driving at 10 mA/cm². When a life test was conducted byconstant-current driving at 10 mA/cm², the luminance half-life was 200hours.

Example 3

A vinyl polymer including3-(4-vinylphenyl)-7,12-diphenylbenzofluoranthene as a monomer unit wassynthesized, and a 2-wt % toluene solution of the vinyl polymer wasprepared in a manner similar to Example 1. Further, tetraphenylbutadienerepresented by the following formula (66) was added as a blue-emittingdopant by a ratio of 2 wt % to the monomer unit in the vinyl polymer, soas to yield a luminescent layer forming coating liquid.

An organic EL element was produced in a manner similar to Example 1except that a luminescent layer was formed by using thus obtainedcoating liquid. The resulting organic EL element yielded blueluminescence due to tetraphenylbutadiene, whereas its current efficiencywas 2.1 cd/A at the time of constant-current driving at 10 mA/cm². Whena life test was conducted by constant-current driving at 10 mA/cm², theluminance half-life was 330 hours.

Example 4

Polyvinylcarbazole represented by the above-mentioned formula (65) andoxadiazole as an electron-transporting molecule represented by thefollowing formula (67) were blended at a ratio of 70:30, and a 2.0-wt %toluene solution of this blend was prepared. Further,poly-1-(4-vinylphenyl)-2,2-(3,7,12-triphenylbenzofluoranthene)-yl-aminewas added by a ratio of 2 wt % to the monomer unit in the vinyl polymer,so as to yield a luminescent layer forming coating liquid.

An organic EL element was produced in a manner similar to Example 1except that a luminescent layer was formed by using thus obtainedcoating liquid. The resulting organic EL element yielded blueluminescence due to the vinyl polymer includingpoly-1-(4-vinylphenyl)-2,2-(3,7,12-triphenylbenzofluoranthene)-yl-amine,whereas its current efficiency was 3.0 cd/A at the time ofconstant-current driving at 10 mA/cm². When a life test was conducted byconstant-current driving at 10 mA/cm², the luminance half-life was 500hours.

Example 5

Into 6.7 mL of tetrahydrofuran (TFF), 0.53 g of3-(4-vinylphenyl)-7,12-diphenylbenzofluoranthene represented by theabove-mentioned formula (7), 0.47 g of N-vinylcarbazole represented bythe above-mentioned formula (54), and 10 mg of benzoyl peroxide (BPO) asa radical polymerization initiator were dissolved, and they were held at70° C. for 48 hours in nitrogen atmosphere, so as to effect apolymerization reaction. After the completion of the reaction,reprecipitation was carried out three times by using THF and methanol asgood and poor solvents, respectively, and then similar reprecipitationwas performed three times with the poor solvent replaced by ethylacetate, whereby 0.6 g of a vinyl copolymer including3-(4-vinylphenyl)-7,12-diphenylbenzofluoranthene (30 mol %) and N-vinylcarbazole (70 mol %) as monomer units was obtained. Theweight-average molecular weight of thus obtained vinyl copolymer was12,000. Subsequently, a 2-wt % toluene solution of the vinyl copolymerwas prepared and employed as a luminescent layer forming coating liquid.

An organic EL element was produced in a manner similar to Example 1except that a luminescent layer was formed by using thus obtainedcoating liquid. The resulting organic EL element yielded blueluminescence due to the fluoranthene structure in the vinyl copolymer,whereas its current efficiency was 2.5 cd/A at the time ofconstant-current driving at 10 mA/cm². When a life test was conducted byconstant-current driving at 10 mA/cm², the luminance half-life was 350hours.

Example 6

A 2.0-wt % toluene solution of the vinyl copolymer was prepared in amanner similar to Example 5, and tetraphenylbutadiene as a dopant forluminescence was added by a ratio of 2 wt % to the monomer unit in thevinyl polymer, so as to yield a luminescent layer coating liquid.

An organic EL element was produced in a manner similar to Example 1except that a luminescent layer was formed by using thus obtainedcoating liquid. The resulting organic EL element yielded blueluminescence due to the fluoranthene structure in the vinyl copolymerand tetraphenylbutadiene, whereas its current efficiency was 2.5 cd/A atthe time of constant-current driving at 10 mA/cm². When a life test wasconducted by constant-current driving at 10 mA/cm², the luminancehalf-life was 400 hours.

Comparative Example 1

An organic EL element was produced in a manner similar to Example 1except that polyvinylcarbazole (PVK) was used in place of the vinylpolymer including 1-(4-vinylphenyl)-4,9-diphenylbenzofluoranthene as amonomer unit. The resulting organic EL element yielded blue luminescencedue to tetraphenylbutadiene, whereas its current efficiency was 1.6 cd/Aat the time of constant-current driving at 10 mA/cm². When a life testwas conducted by constant-current driving at 10 mA/cm², the luminancehalf-life was only 4 hours.

Comparative Example 2

First, a coating liquid containing PEDOT/PSS was applied onto an ITOsubstrate and dried, so as to form a hole transport layer having athickness of 500 Å in a manner similar to Example 1. Subsequently, axylene solution containing 1.5 mass % ofpoly[2-(6-cyano-6-methylheptyloxy)-1,4-phenylene] (CN-PPP with aweight-average molecular weight of 10,000) which was a π-conjugatedpolymer emitting blue fluorescence was applied onto the hole transportlayer, and was dried in vacuum for 1 hour at 180° C., so as to form aluminescent layer having a thickness of 1,000 Å. On the luminescentlayer, a Ca layer (having a thickness of 60 Å) as an electron injectionlayer and an Al layer (having a thickness of 2,500 Å) as an auxiliaryelectrode layer were deposited in vacuum in this order, so as to form acathode layer, and the surface on the cathode layer side was sealed,whereby an organic EL element was obtained.

In thus obtained organic EL element, no luminescence was seen uponconstant-current driving at 10 MA/cm².

Comparative Example 3

Tetraphenylbutadiene was added as a dopant by a ratio of 3 mass % to thesolid content of CN-PPP, so as to prepare a luminescent layer formingcoating liquid. An organic EL element was produced in a manner similarto Comparative Example 2 except that a luminescent layer was formed byusing this coating liquid. The resulting organic EL element yielded blueluminescence, whereas its current efficiency at the time ofconstant-current driving at 10 mA/cm² was less than 0.1 cd/A.

Industrial Applicability

As explained in the foregoing, the organic EL element and organic ELdisplay of the present invention can achieve all of the heat resistance,life, and emission efficiency at high levels, and can stably attainexcellent luminance and color displaying functions for a long period.

1. An organic EL (electroluminescence) element comprising: a substrate;a first electrode layer formed on one side of the substrate; an organiclayer formed on the first electrode layer; and a second electrode layerformed on the organic layer; the organic layer containing a vinylpolymer obtained by polymerizing a polymerizable monomer containing acompound represented by the following general formula (1) or (2):

wherein each of L¹ and L² is a substituted or unsubstituted phenylenegroup; X¹, X², X³, X⁴, X⁵, and X⁶ are either the same or different fromeach other, each referring to alkyl group, alkoxy group, aryl group,aryloxy group, heterocyclic group, amino group, halogen atom, or cyanogroup; each of a and e is 1; each of b, f, g, and h is an integer of 0to 3; c is an integer of 0 to 2; d is an integer of 0 to 4; andsubstituents combined to carbon atoms constituting a fluoranthene ringmay be combined together so as to form a ring.
 2. An organic EL elementaccording to claim 1, wherein the vinyl polymer is obtained bypolymerizing a polymerizable monomer containing a compound representedby the following general formula (3):

wherein L¹is a substituted or unsubstituted phenylene group; X¹, X², andX³ are either the same or different from each other, each referring toalkyl group, alkoxy group, aryl group, aryloxy group, heterocyclicgroup, amino group, halogen atom, or cyano group; a is 1; b is aninteger of 0 to 3; c is an integer of 0 to 2; d is an integer of 0 to 4;and substituents combined to carbon atoms constituting a fluoranthenering may be combined together so as to form a ring.
 3. An organic ELelement according to claim 1, wherein the vinyl polymer is a copolymerof at least one species of the compound represented by one of thegeneral formulae (1) and (2) and at least one species of vinyl monomerhaving a structure different from that of the compound.
 4. An organic ELelement according to claim 1, wherein the organic layer includes aluminescent layer and an electron transport layer formed between a layerin the first or second electrode layer for injecting an electron intothe luminescent layer and the luminescent layer, at least one of theluminescent layer and electron transport layer containing the vinylpolymer.
 5. An organic EL element according to claim 1, wherein theorganic layer further contains a blue-emitting dopant.
 6. An organic ELdisplay comprising: a display part in which a plurality of organic ELelements, each constituted by a substrate, a first electrode layerformed on one side of the substrate, an organic layer formed on thefirst electrode layer, and a second electrode layer formed on theorganic layer, are arranged; a power supply part, electrically connectedto the first and second electrodes, for supplying a voltage or currentto the first and second electrodes; and a switching part for turning onor off the organic EL elements; the organic layer containing a vinylpolymer obtained by polymerizing a polymerizable monomer containing acompound represented by the following general formula (1) or (2):

wherein each of L¹ and L² is a substituted or unsubstituted phenylenegroup; X¹, X², X³, X⁴, X⁵, and X⁶ are either the same or different fromeach other, each referring to alkyl group, alkoxy group, aryl group,aryloxy group, heterocyclic group, amino group, halogen atom, or cyanogroup; each of a and e is 1; each of b, f, g, and h is an integer of 0to 3; c is an integer of 0 to 2;, d is an integer of 0 to 4; andsubstituents combined to carbon atoms constituting a fluoranthene ringmay be combined together so as to form a ring.
 7. An organic EL elementaccording to claim 2, wherein the vinyl polymer is a copolymer of atleast one species of the compound represented by general formula (3) andat least one species of a vinyl polymer having a structure differentfrom that of the compound.